APES – Chapter 24: Air Pollution
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Tommy Hicks
APES – 6th period
Case Study: London Smog and Indonesian Fires
London pollution got extremely hazardous > use headlights in cars at midday in 1952; increased cloud
cover lead to decrease in temperature which led to a higher demand for heat > more fossil fuels
burned
Positive Feedback Loop: increased
Stagnant weather + pollution = recipe for disaster
cloud cover led to reduction in
Sulfur Dioxide and acidic fog adversely affects lungs
temperature which increased demand
Natural gas has since replaced coal > cleaner
for heat which also increased demand
Indonesians practice slash and burn agriculture
for fossil fuels > starts all over again….
o “zero-burn” policy later implemented
Strong El Nino, late monsoon rains, and very dry conditions led to farmers burning lots of land/forest
o Vast amounts of smoke and particulate matter
o People wore masks and had to be treated for illnesses
o Plane crashed killing 234 people
o AQI = Air Quality Index > was 800 (way beyond hazardous)
BOTH of these are examples of human induced air pollution
A Brief History of Air Pollution
The atmosphere has long been a sink for waste disposal.
Long history of recognition of the existence of atmospheric pollutants
o Natural photochemical smog recognized in 1550
o Acid rain first described in 17th century
o Word smog introduced in 1905
 Mixture of smoke and fog
Two events sparked research on air pollution and regulations to control air quality.
o Donora fog in 1948
o London smog event in 1952
o Both cause by pollutants being trapped by weather events. Both killed numerous people.
o Could happen again in cities like Beijing or Mexico City
Stationary Source of Air Pollution
Stationary sources are those that have a relatively fixed location.
o Point sources emit pollutants from one or more controllable sites.
o Fugitive sources generate air pollutants from open areas exposed to wind processes.
o Area sources are well defined areas within which are several sources of air pollutants.
Mobile Source of Air Pollution
Mobile source of air pollutants move from place to place while emitting pollutants.
o Automobiles, trucks, buses, aircraft, ships, and trains.
General Effects of Air Pollution
Affects many aspects of our environment
o Visual qualities
o Vegetation
o Animals
o Soil
o Water quality
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o Natural and artificial structures
o Human health
Significant factor in human death rate for many large cities
o Athens, Greece- # of deaths higher on bad air quality days
o Hungary- 1 in 17 deaths contributed to air pollution
o US- 300,000 deaths/year, health cost $50 billion
o China- health cost $50 - $100 billion
Affect human health in several ways
o Toxic poisoning, cancer, birth defects, eye irritation, and irritation of respiratory system.
o Increased susceptibility to viral infections, causing pneumonia and bronchitis.
o Increased susceptibility to heart disease.
o Aggravation of chronic diseases, such as asthma and emphysema.
Many air pollutants have synergistic effects
o Do greater damage to the lungs than a combination of the two pollutants would be expected to
do based on their separate effects.
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Air Pollutants
200 air pollutants recognized and assessed by US EP and listed in Clean Water Act
o Six called critical pollutants
Primary and Secondary Pollutants
Major air pollutants occur either in gaseous forms or as particulate matter.
Classified as primary or secondary
o Primary pollutants- emitted directly into the air
o Secondary pollutants- produced through reactions between primary pollutants and normal
atmospheric compounds.
In addition to human sources, our atmosphere contains many pollutants of natural origin.
o Release of sulfur dioxide from volcanic eruptions.
o Release of hydrogen sulfide from geysers and hot springs and from biological decay in bogs and
marshes.
o Release of ozone in the lower atmosphere as a result of unstable meteorological conditions.
o Emission of a variety of particles from wildfires and
o windstorms.
o Natural hydrocarbon seeps.
Criteria Pollutants
There are six criteria pollutants
o Sulfur dioxide
o Nitrogen oxides
o Carbon monoxide
o Ozone
o Particulates
o Lead
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Sulfur Dioxide
SO2
o Colorless odorless gas
o Once emitted can be converted to sulfateSO4
o Removed from atmosphere by wet or dry deposition
o Major human sources; coal power plants, industrial processes
Adverse effects depend on dose and concentration present
o Injury or death to animals and plants
o Corrosion of paint and metals
o Important precursor to acid rain
Nitrogen Oxides
Occur in many forms in the atmosphere but largely emitted in two forms:
o Nitric oxide- NO
o Nitrogen dioxide- NO2
 A yellow-brown to reddish-brown gas
 May be converted to NO32o Both subject to emissions regulation and contribute to smog
o NO2 major contributor to acid rain
Nearly all NO2 emitted from human sources
o Automobiles and power plants that burn fossil fuels
Environmental effects
o Irritate eyes and mucous membranes
o Suppress plant growth
 However when convert to nitrate may promote plant growth
Carbon Monoxide
CO is a colorless, odorless gas
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o Even at low concentrations is extremely toxic to humans
 Binds to hemoglobin in blood.
o 90% of CO in atmosphere comes from natural sources
o 10% comes from fires, cars, and incomplete burning of organic compounds
Ozone and Other Photochemical Oxidants
Photochemical oxidants result from atmospheric interactions of nitrogen dioxide and sunlight.
o Most common is ozone- O3
o Colorless gas w/ slightly sweet odor
o Very active chemically, oxidizes or burns
 Beneficial in the upper atmosphere
Because ozone is a secondary pollutant it is difficult to regulate.
o Health standards often exceeded in urban areas
Effects include
o Kills leaf tissue at high concentration
o Damage eyes and respiratory system
o Even young, healthy people may have breathing difficulty on polluted days
Particulate Matter
PM10 is made up of particles less than 10μm in diameter
o Present everywhere but high concentrations and/or specific types dangerous
o Much particulate matter easily visible as smoke, soot, or dust
o Includes airborne asbestos and heavy metals
Of particular concern are very fine pollutants
o PM 2.5- less than 2.5 μm in diameter
o Easily inhaled into the lungs, then absorbed into the bloodstream
o Ultrafine particles- <0.18 μm released by automobiles.
 Related to heart disease
When measured often referred to as total suspended particles (TSPs)
o Tend to be highest in large cities in developing countries
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Recent studies estimate that 2 to 9% of human mortality in cites is associated w/ PM
o Linked to both lung cancer and bronchitis
o Especially hazardous to elderly and those w/ asthma
Dust can be deposited on plants
o Interferes w/ absorption of CO2 and O2 and transpiration
Block sunlight and may cause climate change.
Global dimming
o Gradual reduction in the solar energy that reaches the surface of Earth
o Cools the atmosphere
o Lessens global warming
Lead
Lead is constituent of auto batteries and used to be added to gasoline.
o Lead in gas emitted into air w/ exhaust
o Spread widely around world in soils and water along roadways
o Once in soil can enter the food chain
o Lead now removed from gas in US, CAN, EU
 98% reduction in emissions since 1970s
Air Toxics
Among pollutants that are known or suspected to cause cancer or other serious health problems.
o Associated w/ long-term and short-term exposures
o Gases, metals, and organic chemicals that are emitted in relatively small volumes
o Cause respiratory, neurological, reproductive, or immune diseases
Standards have been set for more than 150 air toxics
o E.g. hydrogen sulfide, hydrogen fluoride, chlorine gases, benzene, methanol, ammonia
o EPA estimates that the average risk for cancer from exposure to air toxics is about 1 in 21,000
Hydrogen sulfide
Highly toxic corrosive gas easily identified by its rotten egg odor.
Produced from
o Natural sources such as geysers, swamps, and bogs
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o Human sources such as industrial plants that produce petroleum or that smelt metals.
Effects of hydrogen sulfide include
o Functional damage to plants
o Health problems ranging from toxicity to death for humans and other animals.
Hydrogen Fluoride
Extremely toxic gaseous pollutant
Released by some industrial activities
o Such as production of aluminum, coal gasification, and burning of coal in power plants.
Even a small concentration (as low as 1 ppb) of HF may cause problems for plants and animals.
o Potentially dangerous to grazing animals because forage plants can become toxic when
exposed to this gas.
Methyl Isocyanate
An ingredient of a common pesticide
o known in the United States as Sevin.
Colorless gas
Causes severe irritation (burns on contact) to eyes, nose, throat, and lungs.
o Breathing the gas in concentrations of only a few ppm causes violent coughing, swelling of the
lungs, bleeding, and death.
o Less exposure can cause a variety of problems, including loss of sight.
Volatile Organic Compounds
Variety of organic compounds used as solvents in industrial processes
o Dry cleaning, degreasing, and graphic arts.
Hydrocarbons
o Comprise one group of VOCs.
o Thousands of hydrocarbon compounds exist, including natural gas, or methane (CH4); butane
(C4H10); and propane (C3H8).
Some VOCs react w/ sunlight to produce photochemical smog
Globally 15% of hydrocarbons emissions are anthropogenic
o In the US 50%
o Primary human source automobiles
Benzene
Additive in gasoline and an important industrial solvent.
Produced when gasoline and coal undergo incomplete combustion.
o Also component of cigarette smoke
o Major environmental source on and off road vehicles
Arcolein
A volatile hydrocarbon that is extremely irritating to nose, eyes, and respiratory system.
Produced from
o Manufacturing processes that involve combustion of petroleum fuels
o Component of cigarette smoke
Variability of Air Pollution
Problems vary in different regions of the country and the world.
o LA pollution mainly from mobile sources
o Ohio and Great Lakes point sources
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Also varies w/ time of year
o Smog a problem in summer when there is lots of sunshine
o Particulates a problem in dry months
Las Vegas: Particulates
Particulates a problem in arid regions
o Where little vegetation is present and wind can easily pick up and transport fine dust.
o Brown haze over Las Vegas partly due to naturally occurring PM 10
o 60% of the dust comes from new construction sites, dirt roads, and vacant land.
Haze From Afar
Air quality concerns are not restricted to urban areas.
o North slope of AK has an air pollution problem that originates from sources in EE and Eurasia.
o Transported by the jet stream.
o Significant as we try to understand global air pollution.
Urban Air Pollution
Whether air pollution develops depends on topography and meteorological conditions
o Determine the rate at which pollutants are transported away and converted to harmless
compounds.
Influences of Meteorology and Topography
Meteorological conditions determine whether air pollution is a nuisance or major health problem.
Primary adverse effect
o Damage to green plants and aggravation of chronic disease
o Usually low-level over long period of time
o However major disaster have occurred
In the lower atmosphere, restricted circulation associated w/ inversion layers may lead to pollution
events.
Atmospheric inversiono Occurs when warmer air is found above cooler air
Occurs primarily in summer and fall
Occurs when cloud cover associated
with stagnant air
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Cities situated in a valley or topographic bowl are more susceptible to smog problems than cities in open
plains.
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Surrounding mountains and inversions prevent pollutants from being transported by wind or weather
systems.
o E.g. Los Angeles
Potential for Urban Air Pollution
Determined by the following factors:
o 1. The rate of emission of pollutants per unit area.
o 2. The downwind distance that a mass of air moves through an urban area.
o 3. The average speed of the wind.
o 4. The elevation to which potential pollutants can be thoroughly mixed by naturally moving air
in the lower atmosphere.
Concentration of pollutants in the air is directly proportional to the first two factors.
o As either emission rate or down wind travel distance increase, so will the concentration of
pollutants
City air pollution decreases w/ increases in third and forth factors.
o The stronger the wind and the higher the mixing layer, the lower the pollution.
Smog
Term first used in 1905 as mixture of smoke and fog that produced unhealthy air.
Two major types
o Photochemical smog (LA type smog or brown air)
o Sulfurous smog (London type smog, gray air, or industrial smog)
Photochemical smog reaction involves sunlight, nitric oxides and VOCs
o Directly related to automobile use
Sulfurous smog is produced by the burning of coal or oil at large power plants.
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Future Trends for Urban Areas
The optimistic view
o Air quality will continue to improve
o Because we know so much about the sources of air pollution and have developed effective
ways to reduce it.
The pessimistic view
o In spite of this knowledge, population pressures and economics will dictate what happens in
many parts of the world,
o The result will be poorer air quality in many locations.
Future Trends for Urban Areas; The United States
LA is a good area to look at for strategies for pollution abatement.
Air quality plan involving the entire urban region includes the following features:
o Strategies to discourage automobile use and reduce the number of cars.
o Stricter emission controls for automobiles.
o A requirement for a certain number of zero-pollutant automobiles (electric cars) and hybrid
cars with fuel cell and gasoline engines.
o A requirement for more gasoline to be reformulated to burn cleaner.
o Improvements in public transportation and incentives for people to use it.
o Mandatory carpooling.
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o Increased controls on industrial and household activities known to contribute to air pollution.
Have focused on LA because the air quality is so poor for a significant portion of the year.
However, many large and not so large US cities have poor air quality
o 30 days per year of unhealthy air resulting from ozone pollution.
Future Trends for Urban Areas; Developing Countries
Less developed countries w/ growing populations are susceptible to air pollution
o Don’t have the financial base necessary to fight air pollution
E.g. Mexico City
o 25 million people
o 50,000 buses, millions of cars, LPG leaks
o In a natural basin w/ mountains surrounding it
o Perfect situation for severe air pollution problem
Attempts to reduce air pollution
o Shutting down oil refinery
o Ordering industrial plants to relocate
Air pollution however will continue to be a problem if unable to control vehicle use and LPG leaks.
Pollution Control
The most reasonable strategies for control have been to reduce, collect, capture, or retain the
pollutants before they enter the atmosphere.
o Reduction of emissions through energy efficiency and conservation measures is preferred.
Pollution Control: Particulates
Particulates emitted from fugitive, point or area stationary sources are much easier to control.
Point and area sources can be controlled by
o Settling chambers or collectors which cause particulates to settle out
Fugitive sources
o Protecting open areas, controlling dust, reducing effects of wind
Pollution Control: Automobiles
Control of pollutants such as carbon monoxide, nitrogen oxides, and hydrocarbons is best achieved
through pollution control for automobiles.
o Nitrogen oxides controlled by recirculating exhaust gas
o CO and hydrocarbons reduced by catalytic converter
Automobile emission regulations plan in US has not been effective
o Pollutants may be low when car is new
o But many people do not maintain them properly
o Suggested that effluent fees replace emission controls
o Other strategies reduce the number or type of cars
Pollution Control: Sulfur Dioxide
Can be reduced through abatement measures performed before, during, or after combustion.
Cleaner coal technology available but makes fuel more expensive.
Switch to low-sulfur coal
o But transportation is an issue
Washing it to remove sulfur
o Iron sulfide settles out
o Ineffective for removing organic sulfur
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Coal gasification
o Converts coal to gas in order to remove sulfur
o Gas obtained is clean
Emissions from power plants can be reduced by removing the oxides from the gases in the stack
o Scrubbing (flue gas desulfurization)
o Occurs after coal is burned
o Gases treated w/ a slurry of lime or limestone
o Reacts to form calcium sulfite
o Can then be process into building materials
Clean Air Act Amendments of 1990
Comprehensive regulations enacted by the U.S. Congress that address acid rain, toxic emissions, ozone
depletion, and automobile exhaust.
Buying and selling of sulfur dioxide emissions
One step back occurred in 2003 when the president and EPA allowed companies to upgrade w/o new
pollution controls.
Also calls for control of
Nitrogen dioxides
o Reduced by 10 million tons
Toxins
o Especially those causing cancer
Ozone depletion in the stratosphere
o End production of all CFCs
Ambient Air Quality Standards
Important because they are tied to emission standards that attempt to control air pollution.
Tougher standards set for ozone and PM 2.5
o When challenged in court justices help that the EPA’s responsibility is to consider benefits to
health not financial costs.
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Air Quality Index
AQI is used to describe air pollution on a given day.
AQI is determined from measurements of the concentration of five major pollutants:
o Particulate matter, sulfur dioxide, carbon monoxide, ozone, and nitrogen dioxide.
An AQI value of greater than 100 is unhealthy.
Air pollution alert is issued if the AQI exceeds 200.
Air pollution warning is issued if the AQI exceeds 300, hazardous to all people.
If the AQI exceeds 400, an air pollution emergency is declared, and people are requested to remain
indoors and minimize physical exertion.
Cost of Air Pollution Control
Cost for incremental control in fossil fuel-burning may be a few hundred dollars per additional ton of
particulates removed.
For aluminum plant, may be several thousand per ton.
Also, a point is reached at which the cost of incremental control is very high in relation to additions
benefits.
Economic analysis of air pollution includes many variables, some of which are hard to quantify. We do
know the following:
o W/ increasing air pollution controls, the capital cost for technology to control air pollution
increases.
o As the controls for air pollution increase, the loss from pollution damages decreases.
o The total cost of air pollution is the cost of pollution control plus the environmental damages of
the pollution.